Hydraulic movement-controlling device



HYDRAULIC MOVEMENT-CONTROLLING DEVICE ...haven-tari N'ejf- M 5mi-th Aug.1', 1944. N v SMITH I 2,354,889

HYDRAULIC MOVEMENT-CONTOLLING DEVICE Aug. 1, 1944. I N V. SMITH2,354,889

l HYDRAULIC MOVEMENT-CONTROLLING DEVICE Filed Jan. 28, 1943 5Sheets-Sheet 5 y i 4+ 49' 2= i .5 6L /2 v 4-7b \3Z 47 v y Patented Aug.1, 1944 assises HYDRAULIC MOVEMENT- CON TROLLING DEVICE Neil V. Smith,Los Angeles,iC'alf., assigner, by` mesne assignments, to Senacon ServiceCompany, Cleveland, Ohio, avpartnership Application January 28, 1943,Serial No. 473,788

17 Claims. l Cl. 188-97) This invention relates to devices forcontrolling the movement of machine parts and relates more particularlyto hydraulic movement-controlling devices. A general object of theinvention is lto provide a practical, effective hydraulicmovementcontrolling device that is small, compact, and entirelyself-contained.

It is often necessary to govern the relative movement of machine toolparts, or the like. A hydraulic cylinder and piston type movement'-checking device is most advantageous for such a purpose, but there arecertain factors that have limited the application of this type ofdevice. It is essential to the proper functioning of the device that theactive end of the cylinder be completely occupied by a substantiallynoncompressible uid and that voids be prevented from developing therein.Movement of the piston rod in either direction, in a simple piston andcylinder structure in which the active end of the cylinder contains asubstantially non-compressible fluid, varies the net capacity of thecylinder and these variations must be compensated for in order to makethe device operative. A balance rod has been used to compensate forthese variations, but the use of a balance rod does not compensate forincidental leakage of liquid, nor for the dinerential in the expansionand contraction of the hydraulic liquid and the sealed cylinder systemresulting from temperature changes. The dilierential in the expansionand contraction of the hydraulic liquid and the cylinder structure, andthe incidental leakage of liquid from the cylinder, develop voids in thesystem and may cause air to nd its Way into the cylinder. vents thebalance rod device from functioning properly.

My co-pending application, Serial No. 473,787, filed January 28, 1943,discloses several forms of hydraulic movement controlling devices whichembody spring loaded or resilient means acting on the liquid in thecylinder to compensate for the incidental leakage of liquid, thediiferenti'al in the expansion and contraction of the liquid andcylinder structure, and for rchanges inthe net capacity of the cylinderresulting from piston rod movement. The yielding compensating' means ofmy co-pending application are not in any case -positively actuated bythe piston rod during vthe 'return stroke of the rod, and may yield as aresult of inertia eiects and friction effectsduring such return stroke,with the result that a reduced pressure is created in the cylinder. Thisreduced pressure makes it necessary to employ a sealing means at thepiston rod to prevent air This prel from being drawn into the cylinder.This vacuum packing adds to the size of the device and increases itscost.

Another object of this invention is to provide a movement controllingdevice of the general characterreferred to that automaticallycompensates for the changes in the net capacity of the cylinder due topiston rod movement, the 'differential in the'expansion and contractionof the liquid and the cylinderA structure dueto temperature changes, andfor the incidental leakage of liquid from the cylinder system. Anotherobject of this invention is to provide a vmovement controlling device ofthe character mentioned embodying a novel piston means that maintainsthe liquid in the cylinder under superatmospheric pressure throughoutits entire operating cycle, that compensates for piston rod movement,incidental leakage of liquid from theV cylinder system, and thediiTerential in the expans-ion and contraction of the liquid andcylinder structure due to temperature changes. Another object of thisinvention is to provide a movement controlling device of the characterreferred to in which the piston means does not create a'reduced ornegative pressure in the cylinder at any phase of the piston stroke.This is highly important because there is no necessity .toprovide avacuum sealing means to seal against la vacuum and prevent the Yinwardleakage of air around the piston rod.

.Another object of this invention is to provide a movement-controllingvdevice of the character Amentioned embodying a single piston rod oper'-atively connected with the two elements of the piston through a slack orlost motion connection Yto positively push one piston element during onestroke of the piston, and to positively draw or pull the other pistonvelement during the other piston stroke, providing for a positive pistonaction in both directions and yet allowing for eX- pansion of the liquiddue to temperature changes and allowing for variations in the netcapacity of the cylinder due to piston rod movement.Y

'Anotherobject of this invention is to provide 'a movement controllingdevice of the character mentioned that may be single lacting and that-may have certain of its Vparts interchanged at 'will so that itiisconditioned to have its active movement resisting stroke in eitherdirection at Will, or if desired, may be made doubleacting to beeffective in resisting movement of the machine part in rboth directions.`The parts may be easily interchanged to bring about this reversal inaction or `double action= after the device has been cona device of thecharacter mentioned that cinV bodies means to facilitate thereplenishing of the liquid in the cylinder asrequired, from time totime, and indicating means which disclose when a suflicient quantity ofliquid has been sup-l plied to the cylinder and when the liquid in thecylinder requires replenishing.

The various objects and features of my invention will be fullyunderstood from the follow'- ing detailed description of typicalpreferred forms and applications of my invention, through'- out whichdescription reference is made to the accompanying drawings, in which:

Fig. 1 is a longitudinal detailed sectional view of one form of theinvention. Fig. 2 is a transverse detailed sectional view taken asindicated by line 2-2 on Fig. 1. Fig. 3 is a'fragmentary external viewof therdevice of Fig. 1. Fig. 4 is a view similar to Fig. 1illustratingv another form of the invention. Fig. 5 is a view similar toFig. 1 illustrating still another form of theV invention. Figs. 6 and '1are transverse detailed sectional views taken as indicated by lines 6 6and 1 1., respectively, on Fig. 5, and Fig. 8 is a fragmentary externalView of the device shown in Fig. 5.

The movement controlling devicesof the invention have many applicationsand may be varied to adapt them for given uses. The devices areparticularly well suited to control the move'- ment of machine toolcutting parts that have pneumatic operating means, and in the drawings Ihave illustrated three typical embodiments of the invention adapted forsuch use. Where employed to control the movement of `a machine toolcutting part operated by a pneumatic means, the hydraulic device of theinvention may be adjusted to resist or oppose the movement with auniform resistance much greater than that resulting from the cuttingtool reaction, thereby assuring a smooth and substantiallyuniform motionof the cutting tool through thefwash piece. When a device of theinvention is single acting it operates to oier a selected degree ofresistance to movement in one direction and to allow substantially freeunrestrained movement in the other direction. When the device is doubleact'- ing it may be adjusted to offer any selected degree of resistanceto movement in either direction.

The form of the invention illustrated in Figs. lV to 3 of the drawingsmay be said to comprise, generally, a cylinder I0, regulable means Ilfor conducting liquid from the inner end ofv Ythe cylinder I0 to theouter end'of the cylinder, means I2 for conducting fluid from the outerend of the cylinder I0 to the vinner end of the cylinder,- a piston rodI3 adapted to be opera'.- tively connected with a moving machine part A,and piston means I4 on the piston rod I3 Opelable in the cylinder I0 andadapted to compensate for differences in the net capacity of thecylinder ID due to movement 'of the rod I3, for the diierentialin theexpansion and contraction of the liquid and the cylinder structlllll@ totemperature changes, and for the incidental leakage of liquid from thecylinder.

The cylinder II) may be a simple, elongate tubular member provided atits inner and outer ends with heads I5 and I6. The end portions of thecylinder I I) are received in annular grooves I1 in the heads I5 and I6and the grooves I1 carry gaskets I8 for sealing with the ends of thecylinder. Simple, effective means is provided for securing the two headsl5 and I6 on the opposite ends of the cylinder. This means includes vaseries of rods I9 screw threaded or otherwise iiXed in openings 20 inthe marginal portions of one head and passing through openings 2| in themarginal portions of the other head. Nuts 22 are screw threaded on therods I9 and clamp against said other head to hold the heads on the endsof the cylinder I0. It will be seen how the end portions of the cylinderI0 are tightly engaged in the grooves I1 when the nuts 22 are tighteneddown. The outer head I6 is preferably provided with a lling opening 23to facilitate the introduction of the liquid to the cylinder. Theopening 23 is normally closed by a gasketed threaded plug 24.

The means I I serves to conduct the liquid from the inner portion of thecylinder I0 to the outer portion of the cylinder during movement of thepiston means I4 in the direction of the arrow in Fig. 1. It will beassumed that this is the active stroke of the piston means I4 and thatthe device is utilized to oier resistance to movement of the machinepart A in this direction. The liquid conducting means II includes a tube25 extending longitudinally of the cylinder I0. The head I5 has alateral boss 2G provided with a socket 21. The head I6 has a smallerboss 28 provided with a similar socket 29. The opposite ends of the tube25 are received in the sockets 21 and 28. in the sockets 21 and 29 toseal about the opposite end portions of the tube 25. A port 3I in thehead I5 leads from the inner end of the cylinder l0 to the adjacent endof the tube 25. A similar port 32 is provided in the head I6 and extendsfrom the outer end of the cylinder I0 to the adjacent end of the tube25.

The means II further includes a throttle valve V for governing the flowof liquid from the inner endto the outer end of the cylinder I9 toresist movement of the part A during the active stroke. The throttlevalve V is carried by the head l5 and controls the flow of liquidthrough the port 3|. The boss 25 has an opening 33 joining the port 3|.A valve seat 34 is engaged in the inner portion of the opening 33 wherethe opening joins the port 3 I The outer portion of the opening 33 isenlarged in diameter and carries packing 35 and a gland 36. A valve stem31 is adjustably screw threaded through the gland 33 and passes inwardlythrough the packing 35. The inner end of the stem 31 opposes the valveseat 34 and is cooperable with the seat to restrict the ilow of liquidthrough the port 3l. An operating knob 38 is provided on the outer endof the stem 31 to facilitate adjustment of the valve stem. The throttlevalve V is readily regulated by means of the knob 38.

The means I2 serves to conduct fluid from the outer end of the cylinderIll to the inner end of the cylinder during the return stroke of thepart A and the piston means I4. The means I2 resembles the means II andincludes a tube 39 extending longitudinally at the exterior of thecylinder I0. The outer head I6 is provided with Packing glands 30 areengaged,

a lateralr boss 4U and the inner head. I5 has a smaller boss 4I.The'opposite ends of the tube 39' are received in sockets 42 in thebosses 40 and 4I" and packing glands.y 43'-v are threaded in the socketsto secure and seall about the opposite ends of the-tube. A por-t44 .inthe head I6 leads from the outer end of the-cylinder II'I` to theadjacent end` of the tube .39- and a similar port 45 inthe head IJ5connectsf` the inner end of the cylinder I with the tube A39. 'A lateralopening 4'6 is providedin theboss 40 of the head I6 to intersect or jointhe port. 44. The vopening 46 isk preferably the same as the above.described opening 33` having an enlarged threaded outer portion.

A valve seat 48 of the same character as the above described seat 34 isarranged in the inner portion of the opening' 45. A check valve 49 isurged inwardly against the seat 48 by a spring '50V which is arranged.under compression between the valve and the inner end of the fitting 41.rIhe valve 49 prevents the flow of liquid through the means I2` duringthe active stroke of thepart A and opens to allow the free flow ofliquid through the means I2 during the return stroke. It will be"observed that the throttle valve. V and the tting. 41v with the relatedcheck valve 49 may be exchanged onev forv the other, that is, they maybe reversed to. reverse the action ofthel device. This will bemore fullydescribed.

A liquid supply fitting 41 is threaded `in the 'enlarged portion of theopening' 46. The fitting 4T may bef in the naturev of a grease gunfitting and is employed to replenish thefliquid of the cylinder IIJ,` aswill be more fully described. The port or passage 4.1'3L through thefitting 41 is provided with a check valve 4'1b which prevents outward owor leakage of liquid from the fitting.

The piston rod I3 is operatively connected-with the machine' partl A byany suitable or selected means and extends through the cylinder head Ito connect with the piston means I4 within the cylinder I-IJ. In. thepreferred construction a bushingror sleeve 5I is secured in a centralopening 52 in the head I5 and projects outwardly from the head. Thesleeve 5I may carry an adjustable mounting nut 53 to facilitate mountingof the device. The piston rod I3 slidably passes through the sleeve 5Ito enter the cylinder I8. Sealing means 54 is provided in the sleeve 5Ito seal about the piston rod. The rod I3 is "tubular for the purpose t0be hereinafter described.

Inl the application of the invention illustrated the rod I3 is equippedto be moved or reciprocated by the machine part A. The part A is in, thenature of a yoke which straddles the rod I3 with clearance. The outerportion of the piston rod I3 is threaded and carries spaced pairs ofnuts 55 to be engaged by the part A.-V It is often desirable ornecessary to' space the pairs of nuts 55 so that there is substantialplay or lost motion between the partA A and the 'spaced sets of nuts.The nuts 55 may be shifted or adjusted to vary the extent of thisslack.p

The piston means I4 is animportant'feature of the invention. The meansI4 is moved or operated by the machine part A through the medium of thepiston rod I3 vand acts on the liquid within the cylinder I0 to force orcirculate the -liquid from one end of the cylinder'to the other. Thecontrol or' restriction of this movement of the liquid by the throttlevalve V controlsv movement of the machine part A. In addition to theconventional piston actionthe pistonmeansl'li under superatmosphericpressure and further serves to compensate for variations in the netcapacity of the cylinder due to piston rod movement, for thedifferential in expansion and contraction of the liquid and the cylinderstructure, and for incidental leakage of liquid from the cylindersystem. These functions of the piston means I4 assure the continuedsuccessful operation of the device.

The piston means I4 includes an enlargement or head 56 on the inner endof the piston rod I3 and two relatively movable piston elements 51 and58 engaged and moved by the head 56. In the simple structure illustratedthe head 56 is in the form of a nut fixed on the inner end of the pistonrod I3. The elements 51 and 58 are arranged at opposite sides of thehead 56, the element 51 being in front of the head and the element 58being behind the head. The piston element 51 is provided at itsperiphery with an annular groove containing a sealing ring 59 forslidably sealing with the wall of the cylinder I0. The piston rod I3 andthe piston element 51 are related for relative movement and the elementhas a central opening 60 slidably receiving the rod. The piston element51 carries means for sealing with the piston rod I3. In practice thepiston element 51 may be cup-shaped to contain a sealing ring assembly62. The sealing ring assembly is held active by a spring 63. The spring63 is held under compression between 'the packing ring assembly 62 and awasher 64 which bears against a ring engaged within the cupshapedelement 51. The piston element 51. has a fiat inner end engageable bythe head 56. When the part A is moved in the direction of the arrow inFig. 1 the head 56 comes into engagement with the element 51 to move thepiston element forwardly in the cylinder I6.

The piston element 58 may be a simple, discvlike part provided at itsperiphery with an annular groove containing a sealing ring 66 forslidably sealing with the wall of the cylinder I0. The inner side of theelement 58, which faces the element 51, mayhave a socket 61 for freelyreceiving the head 56. When the machine part A moves in a directioncounted to the arrow in Fig. 1 the head 56 moves into cooperation withthe elementl 58 to push the element rearwardly through the cylinder I0.

The piston elements 51 and 53 are shaped and are spaced apart so thatthe head 56 and the elementsv have substantial relative movement.Theinvention provides spring means for yieldingly urging the elementsagainst the liquid in the cylinder. A coiled'spring 68 is arranged undercompression between the piston elements 51 and 58. The spring 68 visheldin position through its engagement around the cup-shaped element 51.The spring 68 urges the piston elements 51 andf' apart to maintain theliquid in the cylinder I8 under superatmospheric pressure. The relativemovement' betweenthe piston rod I3 and the piston elements 51 and 58 isampleto compensate for changesfinthenet capacity of .the cylinder I0clue' to`V piston rod movement and for the differential in contractionand expansion of the liquid and the cylinder structure. It will be seenthat `as the quantity or volume of the liquid in thecylinder diminishesdue to leakage, the elements Eland` 53 move a greater distanceapartunder ther action of the spring 68.y With the constructiondescribed above the head 560i the piston rodv I3 is adapted to directlycooperserves to maintain the liquid in the cylinderIIJ .ate with thespring-urged pistonrelements51 and '58 to positively move theelements inthe'cylinder I0, the engagement of the head 56 with the element 51serving to pullthe element through the cylinder while the engagement ofthe head 56 with the element 58 positively pushes the element throughthe cylinder.

The invention includes means for indicating when the liquid requiresreplenishing and for indicating when sufcient, liquid has been added tothe cylinder I at the times of lling and replenishing. This meansincludes a rod B9 iixed to the piston element 58 and extending outwardlythrough the tubular piston rod I3 to project beyond the outer end of therod. An indicating head is fixed on the outer end of the rod 69. Anindicating band 1I is provided on the rod 69 at a point spaced somedistance from the head 10. In initially filling the cylinder I0 the mainbulk of the liquid may be introduced through the opening 23. When theplug 24 has been returned to the opening 23 the balance of the liquid issupplied to the cylinder under pressure through the fitting 41. Thisdelivery of liquid under pressure to the cylinder Ill puts the spring 68under pressure and moves the piston elements 51, and 58 toward oneanother.l As a result the indicating rod 69 is moved outwardly throughthe piston rod I3. When a sufficient quantity of liquid has beensupplied to the cylinder Ill the indicating band 1I becomes visible atthe outer end of the piston rod I3. The appearance of the band 1Iindicates that a suicient quantity of liquid has been supplied to thecylinder I0. If incidental leakage occurs'during the operation of thedevice the spring 68 moves the elements 51 and 58 a greater distanceapart with the result that the rod 69 is moved inwardly in the pistonrod I3. This may continue until the head 10 approaches the outer end ofthe piston rod I3. When the head 10 reaches or approaches the outer endof the piston rod I3 the operator is informed that the supply of liquidin the cylinder Il] requires replenishing.

In the operation of the form of the invention illustrated in Figs. 1, 2and 3 of the drawings the cylinder Ill is supplied with liquid underpressure in the manner described above, and the nuts 55 are adjusted toprovide for the desired drag link connection between the part A and thepiston rod I3. It will be seen that during reciprocation of the part A,the part alternately cornes into engagement with the spaced sets of nuts55 to reciprocate the piston rod I3. During each active stroke of thepart A, that is, during movement of the part A in the direction of thearrow in Fig. 1, the part moves into engagement with the outer set ofnuts 55 to move the piston rod. This movement of the piston rod I3brings the head 56 into engagement with the piston element 51 and thehead engaging with the element 51 obliges the element to move forwardlywith the piston rod. The piston element 51 is positively moved forwardlyin the cylinder to force the liquid in the forward end of the cylinderthrough the means II to the rearV end of the cylinder. The flow ofliquid through the means II is controlled by the throttle valve V.

The valve V may have been previously adjusted to restrict the ow throughthe means II to any selected degree. It will be apparent that regulationof the valve V determines the degree of resistance to movement of thepart A oiered by the device. In practice the valve V may be adjusted tooiler a high degree of resistance to .movement-of the part A in thedirection of the corresponding reference numerals are applied to theircorresponding parts. Y

lopening 11 slidably passing the piston rod I3. Sealing means 18 in theopening 11 slidably seals .arrow in Fig. 1, and this resistance may begreater than the cutting tool reaction'to make the movement of themachine part substantially uniform.

The liquid forced through the means II by the Vforward motion of thepiston element 51 enters the rear end of the cylinder IU and pushes thepiston element 58 forwardly. 1"

Upon the return stroke of the part A the piston rod I3 is moved inwardlyor rearwardly and `the head 56 comes into engagement with 'the otherresilient means that yield because of inertia and friction effects tocreate a reduced presysure in the cylinder I0. Rearward movement of thepiston element 58 forces liquid from the rear end of the cylinder I0through the means I2 to the forward end of the cylinder. The check valve49 opens to allow a substantially free ow of the vliquid through themeans I2, allowing for a rapid free return stroke of the' machine partA.

The action of the device may be readily re'- versed to oii'er controlledor selected resistance to movement of the machine part A in a directioncounter to the arrow in Fig. 1 and to permit free unrestrained returnmovement ofthe machine part. This is accomplished by merely reversingthe positions of the throttle valve V and the fitting 41 with `itsrelated :check valve 49. As above described the openings 43 and 46 arealike so that the throttle valve V and the fitting 41 with its valve 49may be readily exchanged. With the throttle valve V engaged in theopening 46 the valvev may be regulated to restrict the flow through themeans I2`to any lselecteddegree so that outward movement of the pistonelement 58 by the part A, through the medium of the piston rod I3, maybe resisted to the selected extent. During the return stroke, that is,during movement of the part A inthe direction of the arrow in Fig. l,the liquid in the forward end of the cylinder is forced out through themeans II to the rear end of the cylinder, the flow through the means I Ibeing 'substantially unobstructed to allow unrestrained return movementof the part A.

The device of Figs. 1, 2 and 3 of the drawings may be readily madedouble acting. To accomplish this the tting 41 with its related checkvalve 49 is removed from the vopeningll and is replaced by a throttlev'alve V, and check valves are provided in the inlets of the means IIand I2. With the means II and the means' I2 both controlled by athrottle valve V, movement of the machine part A in both directions maybe restrained or controlled as required.

Fig. 4 of the drawings illustrates the device 'of the invention providedwith another form of Ipiston means I 4a.

The cylinder Ill, the KAmeans II and I2, the piston rod I3 and thethrottle valve V may be the same as described above and The piston meansI4a includes two piston elements 15 and 16. The piston element 15 is theforward or inner piston part and has a central about the rod I3. Asealing ring 19 is arranged 7 :in an annular groove in the exterior ofthe pisf tonY element 15 to seal with the wall of the vcylinder I0. Inthisform of the invention the head 80 on uthe inner end of the tubularpiston Lrod I3 is in the form of a disc or flange-and the piston element'I5 may have a socket 8l which receives the head 80 with clearance. Theouter piston element 'I6 may be a simple disc-like-part provided with aperipheral annular groove carrying a sealing ring 82 forslidably-sealing with the wall of the cylinder I0. The indicatingfrod 69is fixed to the piston element Iland extends forwardly to pass throughthe tubular-piston-rod I3 as inthe previously described form fof theinvention. v

The piston element I6 is spaced forwardly from the element I5 and aspring 83 is `arranged under compression between the flange'BO and theelement 16.

for the diierential in the expansion and contraction of the liquid andthe cylinder structure due to temperature changes, and for incidentalyleakage from the cylinder system.

lThe invention provides means for positively transmitting movement fromthe piston rod head 80 to the piston element I6 to protect-the spring83. A tube or s1eeve83f1 is fixed to the head 80 andprojects outwardlyin Vsurrounding relation to the rod B9. The end of thesleeve I83a isengageable with the element L8 only during'movement of the part A in adirection counter to the arrow in Fig. 4, and when the spring 83 iscompressed to a substantial extent.

The operation of the structure illustrated in Fig. 4 is considerablydifferent than that of the previously described embodimentof theinvention. During the active stroke of the part A inv the direction ofthe arrow in Fig. 4 the part contacts the outer set of nuts 55 totransmit movement to the tubular piston rody I3 and the head 80 movesinto engagement with the piston element I5. This engagement results vin`the positive transmissionA of movement to the piston element I5 and theelement is moved forwardly inthe cylinder I0 to force the liquid throughthe means II to the outer end-of the cylinder. The vthrottle valve V maybe adjusted toresist this liquid flow to any extent so that movementofthe machine part A is resisted to the desired degree. When the machinepart Amoves in the direction counter to the arrow in Figpi it cornesinto engagement with theinner set of knuts 55 to transmit movement tothe-tubularpistonrod I3. The head 80 of the piston rod transmits thismovement to the piston element I6 through the sleeve 83a and the pistonelement moving through the cylinder forces-the liquid to ow from therear end ofthe cylinder to the forwardend of the cylinder through themeans` I2. The check valve'49 opens to allow free-unrestricted flow ofthe liquid through the means |2.

The structure of Fig. 4 eliminates the shock or hammer action atthestart of the active stroke resulting from thepistcn rod head mov inginto engagement with the forward piston. element as it may in Figs. `1to 3,1andreduces or eliminates the non-checking or non-effectiveI travelof the piston rod at the start of the activestroke. At the start of thereturn stroke movement is transmitted through the spring 83 to thepiston element 'I6 and the sleeve 83af`does The spring 83 acting againstthe piston element I6 maintains the liquid in fthe f structurev of`Figs."5 "to and fthe.' piston During the return `stroke Athepistonelement 15 tends. to lag, due to tlie diiference inthe frictionalresistance developed by theunequal diameteredfsealing-rings 1B and -I 9.As a result the'head 8-may-move away fromrthe element. At the end ofthereturn stroke-there is some lapseof time before the active strokebegins. During the .return stroke and duringsaid lapse the compressedspr-ing 83pushes-on the liquid in the-rean portion ofthe cylinder,forcing the liquid through they means` I2 tothe forward end of thecylinder. .The :liquid under vpressure thus suppliedto the forward endof Athe cylinder forces the element rearwardlyagainst the head.EAccordingly, at the start of the active-stroke the element 'I5andthehead 80 areV in engagementso that Vnunon-checking vmovement andthe entire stroke of the rrod nI3`is effective in vchecking orcontrollingthe movement of thepart A.

If itis desired Vto reverse =the action'of the device the throttlevalveVis engagedin the boss 4u ofthe outerhead la and thektting' 41 landthe check .valve 4v9 are .engagedin-the boss -26 of the-cylinder headI5. The Aspring-33 is removed and'is eligagedbetween thecylinder'element 'I5 and'thehead of the piston rod I3. lWhen-thesechanges have'been made the head 8U is adapted Yto comeinto-di-rectcontact with thelpi'ston element 16 for the direetftransmisf sionof'movement thereto -when-thepart A--is moved-in therdirection countertofthe arrow-in Fig. 4. Accordingly, the movement is transmit- `teddirectly to the liquid inthe rear or outer portion ofthe cylinder IUfandtheliquidis'forced through the means I2 which is-underthe control of'the' throttle valve`V adjusted to-provide-fory the selectedresistance'to movement yof the, part A'. During the return stroke of.the part A movement istransmittedf from the. piston rod head tothepiston element'15 throughvthe spring 83 element forces lthe liquid fromthe "forward end ofthe cylinder `'through the means II to therear .end vi lo'w'of fluid being substantially unrestricted.

'Inftlie embodiment of the'. invention illustrated inFig's. 5to 8,inclusi-ve, of .the drawings the cyinder I0 "an`d` the means' IIV .an'd,I2- may 'lbe the same asfinv the vpI-eceding -forms .of the inventionanfd' corresponding lreference. numerals are 'appliedto thecorresponding- -r ar'tsf..l l The l8,I inclusive,v is .-character;izedby a piston means Mb havingtwok piston elements Aa5j .fn1rss. andseparate. piston rods As1 and 88'lfo`r` "the respective piston elementsdirectly moved or operated* by the machine irait A.

Ihepiston elements85 and -V86am spaced apart and "are of any selectedconstruction. `In the case illustratedl the elementi/ comprises a bodyor disc"89screwlthreadedon fthe piston rodl, a sealing rirg`90lforslidably. sealing with` the -Wall of"the"cylinder"Ill,l aridablockor nut 9| leather or seal-ing ring 413,y isheld oriclampedvbetweentheldisczand thenllfs. .Y

ICoiledsprisngs .95 areengaged lunder' compression between theAcliscs#teatrali-921` ofrthelpis-ton notfjar' or hammerag'ai'st'thepiston velementjd.e1e11:1en-ts85 andas.; Thesprmgstgsurxgathepis` of the cylinder, this 6 .g-stese ton elements away from oneanother and maintain the liquid in the cylinder l0 under compression.The piston elements 85 and 86 are related for relative movement tocompensate for changes in the-net capacity of the cylinder l0 due tomovement of the piston rod 81 into and out of the cylinder I8, for thedifferential in the expansion and contraction of the liquid and thecylinder structure due to temperature variations, and forincidentalleakage ofvliquid from the cylinder. -The rod 88V of thepiston element 86 extends forwardly to pass through the tubular pistonrod' 81 of the element 85. The rod 88 extends a considerable distancebeyond the outerv end of the rod 81.

lnfthis form of the invention the piston rods 81 and 88 carry means thatare alternately engaged'V by the-machine part A to transmit'movement` totheir respective piston elements 85 and 86. A collar 95 is'screwthreaded on the outer portion of the tubular piston rod 81 and atube 96extends forwardly from the collar.' yA anged nut 91 may removably securethe tube 96 to the c01- lar '95. The tube 96 is externally screwthreaded and is provided' with a set of adjustable nuts 98. The nuts 98are arranged to be engaged by the machine part A when the same moves inthe direction of the arrow in Fig. 5. The nuts 98 may be adjusted alongthe tube 96 to vary the active stroke of the device, that is, to varythe extent of movement ofthe part A that is resisted by the device. L

The tube 98 is provided'with diametrically opposite longitudinal slots99. A nut |00 is adjustably screw-threaded on the rod 88 of the pistonelement 86 and carries two arms Ylill which project outwardly throughthe slots 99.

The arms IDI are spaced-inwardly fromthe nuts 98 and are arranged to beengaged by the machine part A when the same moves in the directioncounter to the arrow'in Fig. 5. The part A. is adapted to engage thearms IDI for the 'directjA transmission of movement to the pistonr rod8'8 and the piston element 86. Upon the removal o'f the-tube se fromaround the nut-lon the nut may be adjusted along the'piston ro'd'188.Thef piston rod 88 projects outwardly beyond the sleeve 96'and isprovided Vwiththe indicating head 10,

and the indicating band 1I'which "are employed in the same manner as inthe previously described forms of the invention.

In the operation of the device illustrated ini Figs. 5 to 8, inclusive',of the drawings the throttle` valve V may be adjusted to provide for'thede''. ,n

sired degree of resistance to movement of the part A and the nuts 98 and|00 maybe adjusted as operating conditions may/require'. When the] partA moves in the direction of the arrow ini Fig. 5 it comes intoengagement with thenuts 98V so that the tubular pistonrod 81 and thepiston', f' element 85 are positively moved. The positivelyjactuatedpiston'element 85 forces the liquid 'from `the forward portion of thecylinder through the means H to the rear portion of the'cylinder, theflowof the liquid being restricted by the throttle valve' V to providethe required degree of resistance to'y movement of the part A. When themachine part A moves in the* direction" counter to' the arrow in Fig. 5it comes mitted directly to the piston" rod 88'andypiston element 86.The positivelyactuated piston' element 86 moves rearwardly through lthecylinder l0 to displace theliquid therefrom through the into engagementvwithi the arms |00 and movement of the part istrans-l This flow ofliquid is si'bstant'ially unrestricted and the movement of the machinepart A is unrestrained. The action of the device of Figs. 5

to 8, inclusive, may be reversed and the device may be made doubleacting in the same manner as the device of Figs. 1 to 3, inclusive.

Having described only typical preferred forms and applications of myinvention, I do not wish to be limited or restricted to the specicdetails herein set forth, but wish to reserve to myself lments to urgeit against the liquid in the cylinder, positive means for transmittingmovement from said part to one of said elements when said part moves inone direction, means for transmitting movement from said part to the iotherfelement during movement of said part in the other direction, meansfor conducting liquid from one end of the cylinder to the other duringmovement of said part in the first named direction, means forrestricting the ow through the last named means to resist movement ofsaid part, and means for conducting liquid from one end of the cylinderto the other during movement of said part in said other direction.

2. A device for controlling the movement of l a reciprocating partincluding a liquid containing cylinder, piston means in the cylinderincluding two relatively movable piston elements, spring means acting onat least one of said elements to urge it against the liquid in theVcylinder, positive means for transmitting movement from said part toone of said elements when said part moves in one direction, means fortransmitting movement from said part to the other element duringmovement of said part in the other direction, means for conductingliquid from one end of the cylinder to the other during movement of saidpart in the rst named direction, throttle valve means for restrictingthe low of liquid through the last named means so that the piston meansresists movement of said part in the rst named direction, and means forconducting liquid from one end of the cylinder to theother duringmovement of said part in the:

other direction.

3. A device for controlling the movement of a reciprocating partincluding a liquid containing cylinder, piston means in the cylinderincluding two relatively movable piston elements, springA means forurging the elements apart so that they are yieldingly urged against theliquid in the L ment, means for conducting liquid from o ne end of thecylinder to the other during movement of said part in one direction,meansfor,controlling,y

the ow of liquid through the last named means isovthat the piston meansresists movement of said part, and means for conducting liquid 'from'one end ofthe cylinder tothe other' during. movement of said part in theother. direction; S v Y v 4 yl.y A device for controlling the movement,of a. means l2' to the'. forward end of the `cylinderf'"ireciprocatingpart including a liquid 'containing aes-inse means-for restricting theflow of the liquid cylinder, piston means in the cylinder including tworelatively movable piston elements, spring means for urging the elementsapart so that they are yieldingly urged against the liquid in thecylinder to subject the same to pressure, means for positivelytransmitting movement in `one direction from said part to one of saidelements andv for positively transmitting movement in the otherdirection from said part to the other element, means for conductingliquid from one end of the cylinder to the other duringvmovement of saidpart in one direction, regulable throttle valve means for controllingthe flow of liquid through the last named means so that the piston meansresists movement of said part, and means for conducting liquid from oneend of the -cylinder to the other during movement of said part in theother direction;

5. A device for controlling the movement of a reciprocating partincluding a liquid containing cylinder, piston means in the cylinderincluding two relatively movable piston elements, spring means forurging the elements apart and against the liquid in the cylinder tosubject the liquid to pressure and yieldable to compensate for changesin the net capacity of the cylinder and for the differential in theexpansion of the liquid and cylinder due to temperature changes, pistonrod means for positively transmitting movement from said part to one ofthe elements during movement of said part in one direction and forpositively transmitting movement from said part to the otherelement-during movement of said element in the other direction, meansfor conducting liquid from one end of the cylinder to the lother duringmovement of the piston means, and valve means for controlling the flowof liquid through the last named means so that movement of saidpart isresisted.

6. A device for controlling the movement of a reciprocating partincluding a liquid containing cylinder, piston means in the cylinderincluding two relatively movable piston elements, spring means forurging the elements apart so that they exert a yielding pressure on theliquid in the cylinder, a piston rod reciprocated by said part, a headon the rod between said elementsmovable into engagement with one elementtov move t-he same when said part moves'in one direction and movableinto engagement with the other element to crnove the same when said partmoves in the other direction, means for conducting liquid between theopposite ends oi'the cylinder during movement of the piston means, andmeans forrestricting the flow of the liquid between the ends of thecylinder in at least one direction so that the movement of said part iscontrolled.

7. A device for controlling the movement of a reciprocating partincluding a liquid containing cylinder, piston means in the cylinderincluding two relatively movable piston elements, spring means forurging the elements apart so that they exert a yielding pressure on theliquid in the cylinder, said elements being spaced apart and the springmeans including a spring engaged between the elements, a piston rodreciprocated by said part, a head on the rod between said elementsmovable into engagement with one element to move the same when said partmoves in one direction and movable into engagement with the otherelement to move the same when said part moves in the other direction,means for conducting liquid between the opposite ends of the cylinderduring movement of the piston means, and

tween the ends of the cylinder in at least one direction so that themovement of said part is controlled. i

8. A device for controlling the movement of a reciprocating partincluding a liquid containing cylinder, piston means in the cylinderincluding two relatively movable piston elements, spring means forurging the elements apart so that they exert a yielding pressure on theliquid in the cylinder, a piston rod reciprocated by said part, a headon the rod between said elements movable into engagement with oneelement to move the same when said part moves in one direction andmovable into engagement with the other element to move the same whensaid part movesin the other direction, separate means for conductingliquid from one end of the cylinder to the other, and regulable meansfor restricting the flow of liquid through at least one of said separatemeans to control movement of said part. v 9. A device'for controllingthe movement of a reciprocating part including a liquid containingcylinder, piston means in the cylinder including two relatively movablepiston elements, the elements being spaced one from the other, -a springengaged between said elements for yieldingly urging them. apart tomaintain the liquid under pressure, a piston rod reciprocated by said-part and entering the cylinder, a head on the rod between said elementsfor alternately engaging said elements during reciprocation of the rodto move the elements through the cylinder, two separate means forconducting iluid between the opposite ends of the cylinder, valve meansfor restricting the flow through one of said separate means to resistmovement of said part in one direction, and check valve means in theother of said separate means allowing the flow of liquid during movementof said part in the other direction. 1

l0, A device for controlling the movement of a reciprocating partincluding a liquid containing cylinder, piston means in the cylinderincluding two relatively movable piston elements, the elements beingspaced one from the other, a spring engaged between said elements foryieldingly urging them apart to maintain the liquid under pressure, apiston rod reciprocated by said part and entering the cylinder, a headon the rod between said elements for alternately engaging said elementsduring reciprocation of the rod to move the elements through thecylinder, two separate means for conducting fluid between the oppositeends of the cylinder, valve means for restricting the ow through one ofsaidseparate means -to resist movement of said part in one direction,and check valve means in the` other of said separate means allowing theflow of liquid during movevment of said part in the other direction,said valve means and check valve being exchangeable one for the other toreverse the action ofthe device.

1l. A device for controlling the movement of a reciprocating partincluding a liquid containing cylinder, piston means in the cylinderincluding two relatively movable piston elements, a piston rodreciprocated by said part and extending into the cylinder, a head on therod between the elements engageable with one element to positively movethe same when said part moves in one direction, means for conductingliquid from one end of the cylinder to the other during such movement ofsaid element, means for restricting the last named means to resistmovement of said part, a spring engaged between the head and the otherelement Vfor transmittingY movement to saidother element, and means forconducting fluid from one end of the cylinder to the other duringmovement of said other element.

12. A device for controlling the movement of a reciprocating partincluding a liquid containing cylinder, piston means in the cylinderincluding two relatively movable piston elements, a piston rodreciprocated by said part and extending into the cylinder, a head on therod between the elements engageable with one element to positively movethe same when said part moves in one direction, means for conductingliquid fromv one end ofthe cylinder to the other during such movement ofsaid element, means for restricting the last named means to resistmovement ,of said part, a spring engaged between the head and the otherelement for transmitting movement to said other element and foryieldingly urging said other element against the liquid in the cylinderto maintain the liquid under pressure, andmeans `for conducting fluidfrom one end of the cylinder to the other during movement of said otherelement. 13. A device for controlling the movement of a reciprocatingpart including aliqud containing cylinder, piston means in the cylinderincluding two relatively movable piston elements, a piston rodreciprocated by said part and extending int-o the cylinder, a head onthe rod between the elements engageable with one element to positivelymove the same when said part moves in one direction, means forconducting liquid from one end of the cylinder to the other during suchmovement of said element, manually regulable valve means for restrictingthe last named means to resist movement of said part, a spring engagedbetween the head and the other element for transmitting movement to saidother element, and means for conducting iiuid from one end of thecylinder to the other during movement of said other element.

14. A device for controlling the movement of a. reciprocating partincluding aliquid containing cylinder, piston means in the cylinderincluding two relatively movable piston elements, and a spring engagedbetween the elements yieldingly urging them against the liquid in thecylinder, a tubular piston rod on one element extending from thecylinder, a piston rod on the other element extending through thetubular rod, members on the rods alternately engaged by said parts totransmit movement to said elements, separate means for conducting'liquidbetween the ends of the cylinder, and means for `limiting the flowthrough one of the last named means to resist movement of said part.

' 15.A device for controlling the movement of a reciprocating partincluding a liquid containing cylinder, piston means 'in the cylinderincluding means for conducting liquid between the ends of the cylinder,and regulable valve means for limiting therflow through one of the lastnamed means to resist movement of said part.

16. A device for controlling the movement of a reciprocating partincluding a liquid containing cylinder',V piston means in the cylinderincluding two relatively movable pistonl elements, spring means actingon at least one of said elements to urge it against the liquid in thecylinder, positive meanswfor transmitting movement from said part to oneof said elements when said part moves in one direction, means fortransmitting movement from said part to the other element duringmovementof said part in the other direction, meansfor conductingliquidfrom one end of the cylinder to the other during movement of said partin the first nameddirection, means for restricting the flow through thelast named means to resist movement of said part, means for conductingliquid from one end of the cylinder to the i other during movement ofsaid part in the other direction, and means for indicating the quantityof liquid in the cylinder. v

1 7. A device for controlling the movement of a reciprocating partincluding a liquid containing cylinder,` piston means in the cylinderincluding two relatively movable piston elements, spring means acting onat leastone of said elements to urge it against the liquid in thecylinder, positive means for transmitting movement from said part to oneof said-,elements when said part moves in one direction, means fortransmitting movement from said part to the other element duringmovement of said part inthe other direction, means forv conductingliquid from one end of the cylinder to the other during movement of saidpart in the rst named direction, means for restricting the flow throughthe last named means to resist movement of said part, means forconducting liquid from one end of the cylinder to the other duringmovement of said part in the other direction, and

meansv for indicating the quantity of liquid in the cylinder includingan indicating rod on one of said elements extending from the cylinder.

1 NEIL V. SMITH.

